kern/68081: [headers] [patch] sys/time.h (lint fix)

[Bruce Evans]

On Sat, 21 Jun 2008, Garrett Cooper wrote:

> Haven't used lint(1) before, but I don't think this is an issue (at
> least not on 8-CURRENT):

All these bugs (in lint, not in the source code) seem to be unchanged
in -current.  You probably tested on amd64, where the proposed fix has
no effect except to add even more style bugs than on i386.

tv_nsec has type long on all machines, and lint doesn't like assigning
uint64_t's to longs when uint64_t is longer than long.  On amd64,
uint64_t is u_long so the assignment doesn't reduce the size, and lint
is apparently too stupid to warn about the sign mismatch.  On i386,
uint64_t is u_long_long, so the assignment reduces the size.

lint is too stupid to understand that right-shifting a 64-bit type
makes it fit in a 32-bit type, except possibly for the sign.  A slightly
more detailed static analysis shows that the value is non-negative,
(in fact that it is between 0 and 10^9-1 inclusive, as is required for
a valid tv_nsec), so there is no problem with the sign.  These stupidities
are bugs in lint, since casting down produces more than enough
non-spurious warnings.  gcc is smarter, but similar warnings in gcc are
normally not enabled.

The proposed fix adds the following style bugs:
all:
- long lines
- explicitly cast the type down, but to a wrong type (uint32_t) instead of
   long, so the full set of conversions is uint64_t -> uint32_t -> long.
   This is a bit harder to understand.  If lint remains stupid but warns
   about sign mismatches too, then this should suppress the warning
   about the size reduction but not a new one about the sign mismatch.
amd64 and some others:
- the full set of conversions now gives a promotion from uint32_t to long.

> [gcooper at optimus /devel/ncvs/src]$ lint time_test.c
> time_test.c:
> _types.h(60): warning: struct __timer never defined [233]
> _types.h(61): warning: struct __mq never defined [233]
> _pthreadtypes.h(44): warning: struct pthread never defined [233]
> _pthreadtypes.h(45): warning: struct pthread_attr never defined [233]
> _pthreadtypes.h(46): warning: struct pthread_cond never defined [233]
> _pthreadtypes.h(47): warning: struct pthread_cond_attr never defined [233]
> _pthreadtypes.h(48): warning: struct pthread_mutex never defined [233]
> _pthreadtypes.h(49): warning: struct pthread_mutex_attr never defined [233]
> _pthreadtypes.h(51): warning: struct pthread_rwlock never defined [233]
> _pthreadtypes.h(52): warning: struct pthread_rwlockattr never defined [233]
> _pthreadtypes.h(53): warning: struct pthread_barrier never defined [233]
> _pthreadtypes.h(54): warning: struct pthread_barrier_attr never defined [233]
> _pthreadtypes.h(55): warning: struct pthread_spinlock never defined [233]
> _pthreadtypes.h(75): warning: struct pthread_barrierattr never defined [233]
> time.h(59): warning: static function bintime_addx unused [236]
> time.h(70): warning: static function bintime_add unused [236]
> time.h(82): warning: static function bintime_sub unused [236]
> time.h(108): warning: static function bintime2timespec unused [236]
> time.h(116): warning: static function timespec2bintime unused [236]
> time.h(125): warning: static function bintime2timeval unused [236]
> time.h(133): warning: static function timeval2bintime unused [236]
> time.h(152): warning: struct sigevent never defined [233]
> lint: cannot find llib-lc.ln

These warnings are due to different sets of bugs in lint:
- lint still doesn't understand the C90 or earlier feature of incomplete
   struct types.  Incomplete struct types are useful and are common in
   headers, so lint shouldn't warn about them.
- lint still doesn't understand the gnu89/C99 feature of "static inline".
   This feature is even more useful though less common in headers than
   incomplete struct types.
- lint libraries seem to have never been configured quite right, so
   llib-lc.ln doesn't exist.  FreeBSD only has llib-stdc.ln and
   llib-posix.ln, and these seem to be far too small to be complete.

Bruce